Injection blow molding processes to manufacture containers are known in the art. An example of an injection blow molding product and method is shown in U.S. Pat. No. 4,540,543 (the '543 patent). This patent describes a process and apparatus to make hollow articles using a combination of injection and blow molding technology. The '543 patent describes, among other things, a process for the high speed manufacture of thin-walled plastic drinking cups of generally known configuration.
Plastic cups made from the process disclosed in the '543 patent are popular as they can be made at high speeds on a commercial level and are relatively strong and flexible. However, they suffer from the inconvenience that once a lid member is placed on the cup to achieve a secure grip, the lid member is difficult to remove.
The difficulty in removing the lid member is caused by the shape of the lip surface with which the lid member engages. The lip surfaces of these prior art cups have square or rectangular cross sections which make the removal of the lid difficult.
In light of the foregoing, there is a need for an injection blow molded plastic container to which a lid can be securely fastened and, when necessary, easily removed.